The prior art discloses many problems associated with formulating and preparing fabric conditioning formulations. See, for example, U.S. Pat. No. 3,904,533, Neiditch et al. issued Sep. 9, 1975. Japanese Laid Open Publication 1,249,129, filed Oct. 4, 1989, discloses a problem with dispersing fabric softener actives containing two long hydrophobic chains interrupted by ester linkages ("diester quaternary ammonium compounds") and solves it by rapid mixing. U.S. Pat. No. 5,066,414, Chang, issued Nov. 19, 1991, teaches and claims compositions containing mixtures of quaternary ammonium salts containing at least one ester linkage, nonionic surfactant such as a linear alkoxylated alcohol, and liquid carrier for improved stability and dispersibility. U.S. Pat. No. 4,767,547, Straathof et al., issued Aug. 30, 1988, claims compositions containing either diester, or monoester quaternary ammonium compounds where the nitrogen has either one, two, or three methyl groups, stabilized by maintaining a critical low pH of from 2.5 to 4.2.
U.S. Pat. No. 4,401,578, Verbruggen, issued Aug. 30, 1983 discloses hydrocarbons, fatty acids, fatty acid esters, and fatty alcohols as viscosity control agents for fabric softeners (the fabric softeners are disclosed as optionally comprising ester linkages in the hydrophobic chains). WO 89/115 22-A (DE 3,818,061-A; EP-346,634-A), with a priority of May 27, 1988, discloses diester quaternary ammonium fabric softener components plus a fatty acid. European Pat. No. 243,735 discloses sorbitan esters plus diester quaternary ammonium compounds to improve dispersions of concentrated softener compositions.
The art also teaches compounds that alter the structure of diester quaternary ammonium compounds by substituting, e.g., a hydroxy ethyl for a methyl group or a polyalkoxy group for the alkoxy group in the two hydrophobic chains. Specifically, U.S. Pat. No. 3,915,867, Kang et al., issued Oct. 28, 1975, discloses the substitution of a hydroxyethyl group for a methyl group. A softener material with specific cis/trans content in the long hydrophobic groups is disclosed in Jap. Pat. Appln. 63-194316, filed Nov. 21, 1988. Compounds with alkoxy, acyloxy, and alkyl groups are disclosed in, e.g., U.S. Pat. No. 4,923,642, Rutzen et al., issued May 8, 1990.
U.S. Pat. No. 4,844,823, Jaques et al., issued Jul. 4, 1989, teaches fabric softener compositions containing, as one option, 3% to 20% diester quaternary ammonium compound, as in U.S. Pat. No. 3,915,867, supra, and fatty alcohol to improve softening performance.
Diester quaternary ammonium compounds with a fatty acid, alkyl sulfate, or alkyl sulfonate anion are disclosed in European Pat. No. 336,267-A with a priority of Apr. 2, 1988. European Pat. No. 418,273, with a priority date of May 22, 1988, discloses, e.g., diester quaternary ammonium compounds and DTDMAC (ditallow dimethyl ammonium chloride) for improved release from a substrate in an automatic clothes dryer.
U.S. Pat. No. 4,923,642, Rutzen et al., issued May 8, 1990, discloses ester fabric softener materials, but with a different fatty acid, i.e., one that is etherified. (The fatty acid is substituted with hydroxy, alkoxy, etc. groups.)
Ger. Offen. 1,935,499, Distler et al., published Jan. 14, 1971, discloses the reaction of fatty acid methyl esters with alkyl diethanolamine and quaternized by methyl sulfate to create a diester quaternary ammonium fabric softener.
U.S. Pat. No. 4,456,554, Walz et al., issued Jun. 26, 1984, discloses alkyl diacyloxyalkyl amines quaternized by trialkyl phosphonates or phosphites.
Ger. Offen. DE 638,918, Henkel, published May 18, 1988 as EP 267,551-A, discloses diester quaternary ammonium compounds in which the fatty acid is substituted by a hydroxy fatty acid.
E.P. Pat. Appln. 284,036-A, Hofinger et al., published Mar. 23, 1988, discloses preparation of diester quaternary ammonium compounds by reacting alkanolamine with a glyceride. (The German equivalent is DE 3710064).
U.S. Pat. No. 4,808,321, Walley, issued Feb. 28, 1989, teaches fabric softener compositions comprising monoester analogs of ditallow dimethyl ammonium chloride which are dispersed in a liquid carrier as sub-micron particles through high shear mixing, or particles can optionally be stabilized with emulsifiers such as nonionic C14-18 ethoxylates.
Ger. Offen. 8,911,522, Volkel et al., published May 27, 1988, describes aqueous fabric softener compositions with a diester quaternary ammonium compound having two C.sub.10 to C.sub.22 acyloxyalkyl chains and a fatty acid.
Ger. Offen. 9,101,295, Trius et al., published Jul. 17, 1989, describes a process to prepare diester quaternary ammonium compounds by reacting alkanolamine and fatty acid. Thereafter, the amine is alkylated to form the quaternary compound.
E.P. Appln. 336,267, Rutzen et al., with a priority date of Apr. 2, 1988, and published Oct. 11, 1989, discloses diester quaternary ammonium compounds having at least one hydroxyalkyl group.
E.P. Appln. No. 91201887.6, Demeyere et al., filed Jul. 8, 1991, teaches perfume/active mixes adsorbed on finely divided silica.
E.P. Appln. 243,735, Nusslein et al., published Nov. 4, 1987, discloses sorbitan ester plus diester quaternary ammonium compounds to improve dispersibility of concentrated dispersions.
E.P. Appln. 409,502, Tandela et al., published Jan. 23, 1991, discloses, e.g., ester quaternary ammonium compounds, and a fatty acid material or its salt.
E.P. Appln. 240,727, Nusslein et al., priority date of Mar. 12, 1986, teaches diester quaternary ammonium compounds with soaps or fatty acids for improved dispersibility in water.
U.S. Pat. No. 4,874,554, Lange et al., issued Oct. 17, 1989, discloses diester quaternary ammonium compounds having polyethoxy groups and the process of making these compounds for use in hair cosmetic preparations.
All of the above patents and patent applications are incorporated herein by reference.